Re: [RFC v2 1/1] memory: Delete assertion in memory_region_unregister_iommu_notifier

[Peter Xu]

On Fri, Jul 03, 2020 at 03:24:19PM +0800, Jason Wang wrote:
> 
> On 2020/7/2 下午11:45, Peter Xu wrote:
> > On Thu, Jul 02, 2020 at 11:01:54AM +0800, Jason Wang wrote:
> > > So I think we agree that a new notifier is needed?
> > Good to me, or a new flag should be easier (IOMMU_NOTIFIER_DEV_IOTLB)?
> 
> 
> That should work but I wonder something as following is better.
> 
> Instead of introducing new flags, how about carry the type of event in the
> notifier then the device (vhost) can choose the message it want to process
> like:
> 
> static vhost_iommu_event(IOMMUNotifier *n, IOMMUTLBEvent *event)
> 
> {
> 
> switch (event->type) {
> 
> case IOMMU_MAP:
> case IOMMU_UNMAP:
> case IOMMU_DEV_IOTLB_UNMAP:
> ...
> 
> }

Looks ok to me, though imo we should still keep the registration information,
so VT-d knows which notifiers is interested in which events.  E.g., we can
still do something like vtd_as_has_map_notifier().

So these are probably two different things: the new IOMMU_NOTIFIER_DEV_IOTLB
flag is one as discussed; the other one is whether we would like to introduce
IOMMUTLBEvent to include the type, so that we can avoid introduce two notifiers
for one device majorly to identify dev-iotlb from unmaps.

Thanks,

-- 
Peter Xu